Polycrystalline group III metal nitride with getter and method of making

ABSTRACT

A gettered polycrystalline group III metal nitride is formed by heating a group III metal with an added getter in a nitrogen-containing gas. Most of the residual oxygen in the gettered polycrystalline nitride is chemically bound by the getter. The gettered polycrystalline group III metal nitride is useful as a raw material for ammonothermal growth of bulk group III nitride crystals.

This application is a continuation-in-part of U.S. patent applicationSer. No. 12/634,665, filed on Dec. 9, 2009, now allowed, which claimspriority to U.S. Patent Application No. 61/122,332, filed on Dec. 12,2008, each of which is incorporated by reference in its entirety.

BACKGROUND

The present disclosure generally relates to processing of materials forgrowth of crystals. More particularly, the present disclosure provides acrystalline nitride material suitable for use as a raw material forcrystal growth of a gallium-containing nitride crystal by an ammonobasicor ammonoacidic technique, but there can be others. In otherembodiments, the present disclosure provides methods suitable forsynthesis of polycrystalline nitride materials, but it would berecognized that other crystals and materials can also be processed. Suchcrystals and materials include, but are not limited to, GaN, AN, InN,InGaN, AlGaN, and AlInGaN, and others for manufacture of bulk orpatterned substrates. Such bulk or patterned substrates can be used fora variety of applications including optoelectronic devices, lasers,light emitting diodes, solar cells, photoelectrochemical water splittingand hydrogen generation, photodetectors, integrated circuits, andtransistors, among other devices.

Gallium nitride containing crystalline materials serve as substrates formanufacture of conventional optoelectronic devices, such as blue lightemitting diodes and lasers. Such optoelectronic devices have beencommonly manufactured on sapphire or silicon carbide substrates thatdiffer in composition from the deposited nitride layers. In theconventional Metal-Organic Chemical Vapor Deposition (MOCVD) method,deposition of GaN is performed from ammonia and organometallic compoundsin the gas phase. Although successful, conventional growth ratesachieved make it difficult to provide a bulk layer of GaN material.Additionally, dislocation densities are also high and lead to pooreroptoelectronic device performance.

Growth of nitride crystals by ammonothermal synthesis has been proposed.Ammonothermal crystal growth methods are expected to be scalable, asdescribed by Dwilinski, et al. (J. Crystal Growth 310, 3911 (2008)), byEhrentraut, et al. (J. Crystal Growth 305, 204 (2007)), by D'Evelyn, etal. (J. Crystal Growth 300, 11 (2007)), and by Wang, et al. [CrystalGrowth & Design 6, 1227 (2006)]. The ammonothermal method generallyrequires a polycrystalline nitride raw material, which is thenrecrystallized onto seed crystals. An ongoing challenge ofammonothermally-grown GaN crystals is a significant level of impurities,which cause the crystals to be colored, e.g., yellowish, greenish,grayish, or brownish. The residual impurities may cause opticalabsorption in light emitting diodes fabricated on such substrates,negatively impacting efficiency, and may also affect the electricalconductivity and/or generate stresses within the crystals. One source ofthe impurities is the polycrystalline nitride raw material.

For example, gallium nitride crystals grown by hydride vapor phaseepitaxy, a relatively more expensive, vapor phase method, havedemonstrated very good optical transparency, with an optical absorptioncoefficient below 2 cm⁻¹ at wavelengths between about 405 nanometers andabout 620 nanometers (Oshima, et al., J. Appl. Phys. 98, 103509 (2005)).However, the most transparent ammonothermally-grown gallium nitridecrystals of which we are aware were yellowish and had an opticalabsorption coefficient below 5 cm⁻¹ over the wavelength range betweenabout 465 nanometers and about 700 nanometers (D'Evelyn, et al., J.Crystal Growth 300, 11 (2007) and U.S. Pat. No. 7,078,731).

Several methods for synthesis of polycrystalline nitride materials havebeen proposed. Callahan, et al. (MRS Internet J. Nitride Semicond. Res.4, 10 (1999); U.S. Pat. No. 6,406,540)proposed a chemical vapor reactionprocess involving heating gallium metal in a vapor formed by heatingNH₄Cl. Related methods have been discussed by Wang, et al. [J. CrystalGrowth 286, 50 (2006)) and by Park, et al. [U.S. Application PublicationNos. 2007/0142204, 2007/0151509, and 2007/0141819). The predominantimpurity observed was oxygen, at levels varying from about 16 to about160 parts per million (ppm). The chemical form of the oxygen was notspecified. An alternative method, involving heating in ammonia only andproducing GaN powder with an oxygen content below 0.07 wt %, wasdisclosed by Tsuji (U.S. Publication No. 2008/0193363). Yet anotheralternative method, involving contacting Ga metal with a wetting agentsuch as Bi and heating in ammonia only, producing GaN powder with anoxygen content below 650 ppm, has been disclosed by Spencer, et al.(U.S. Pat. No. 7,381,391).

What is needed is a method for low-cost manufacturing of polycrystallinenitride materials that are suitable for crystal growth of bulk galliumnitride crystals and do not contribute to impurities in the bulkcrystals.

SUMMARY

Disclosed herein are techniques related to processing of materials forgrowth of crystals are provided. More particularly, the presentdisclosure provides a crystalline nitride material suitable for use as araw material for crystal growth of a gallium-containing nitride crystalby an ammonothermal technique, including ammonobasic or ammonoacidictechnique, but there can be others. In other embodiments, the presentdisclosure provides methods suitable for synthesis of polycrystallinenitride materials, but it would be recognized that other crystals andmaterials can also be processed, including single crystal materials.Such crystals and materials include, but are not limited to, GaN, AN,InN, InGaN, AlGaN, and AlInGaN, and others for manufacture of bulk orpatterned substrates. Such bulk or patterned substrates can be used fora variety of applications including optoelectronic devices, lasers,light emitting diodes, solar cells, photoelectrochemical water splittingand hydrogen generation, photodetectors, integrated circuits, andtransistors, among other devices.

In a specific embodiment, the present disclosure provides a compositionfor a material. The composition includes a polycrystalline group IIImetal nitride material having a plurality of grains. Preferably, theplurality of grains are characterized by a columnar structure. In aspecific embodiment, one or more of the grains have an average grainsize in a range of from about 10 nanometers to about 10 millimeters. Thecomposition has an atomic fraction of a group III metal in the group IIImetal nitride in a range of from about 0.49 to about 0.55. In one ormore embodiments, the metal in the group III metal nitride is selectedfrom at least aluminum, indium, or gallium. The composition also has anoxygen content in the group III metal nitride material provided as agroup III metal oxide or as a substitutional impurity within a group IIImetal nitride less than about 10 parts per million (ppm).

In an alternative specific embodiment, the present disclosure provides amethod for forming a crystalline material. The method includes providinga group III metal in at least one crucible. Preferably, the group IIImetal comprises at least one metal selected from at least aluminum,gallium, and indium. The method includes providing a getter at a levelof at least 100 ppm with respect to the group III metal. In a specificembodiment, the getter comprises at least one of alkaline earth metals,boron, carbon, scandium, titanium, vanadium, chromium, yttrium,zirconium, niobium, rare earth metals, hafnium, tantalum, and tungsten.The method also includes providing the group III metal in a crucible andproviding the getter into a chamber. This chamber and associatedcomponents may also be referred to more generally as a reactor or anapparatus. The method transfers a nitrogen-containing material into thechamber and heats the chamber to a determined temperature. The methodincludes pressurizing the chamber to a determined pressure andprocessing the nitrogen-containing material with the group III metal inthe chamber. In one or more embodiments, the method forms apolycrystalline group III metal nitride in at least the crucible thatcontained the group III metal. In one or more embodiments, the methodforms a polycrystalline group III metal nitride within the chamber,which may substantially occur within the chamber in one or more regionsthat do not include the group III metal crucible.

In yet an alternative specific embodiment, the present disclosureprovides an alternative method of forming a group III metal nitridecontaining substrate. The method includes providing a group III metal asa source material, which comprises at least one metal selected from atleast aluminum, gallium, and indium. The method includes providing agetter at a level of at least 100 ppm with respect to the group IIImetal source material and providing the group III metal source materialand the getter into a chamber. The method also includes transferring anitrogen-containing material into the chamber and heating the chamber toa determined temperature. In a specific embodiment, the method includespressurizing the chamber to a determined pressure and processing thenitrogen-containing material with the group III metal source material inthe chamber. In one or more embodiments, the method forms a crystallinegroup III metal nitride characterized by a wurtzite structuresubstantially free from any cubic entities and an optical absorptioncoefficient of about 2 cm⁻¹ and less at wavelengths between about 405nanometers and about 750 nanometers.

Still further, the present disclosure provides a gallium nitridecontaining crystal. The crystal has a crystalline substrate memberhaving a length greater than about 5 millimeters and a substantiallywurtzite structure characterized to be substantially free of othercrystal structures. In a specific embodiment, the other structures areless than about 1% in volume in reference to a volume of thesubstantially wurtzite structure. The crystal also has an impurityconcentration greater than 10¹⁵ cm⁻¹ of at least one of Li, Na, K, Rb,Cs, Ca, F, Br, I, and Cl and an optical absorption coefficient of about2 cm⁻¹ and less at wavelengths between about 405 nanometers and about750 nanometers.

In certain embodiments, methods of preparing a polycrystalline group IIImetal nitride material are provided, comprising: providing a sourcematerial selected from a group III metal, a group III metal halide, or acombination thereof into a chamber, the source material comprising atleast one metal selected from at least aluminum, gallium, and indium;providing a getter at a level of at least 100 ppm with respect to thesource material into the chamber such that the getter contacts the gsource material; transferring a nitrogen-containing material into thechamber; heating the chamber to a determined temperature; pressurizingthe chamber to a determined pressure; processing the nitrogen-containingmaterial with the source material in the chamber; and forming apolycrystalline group III metal nitride material.

In certain embodiments, methods of forming a polycrystallinegallium-containing group III metal nitride material are provided,comprising: providing a gallium-containing group III metal or a groupIII metal halide source material to a chamber, the gallium-containinggroup III metal or metal halide source material comprising at least onemetal selected from aluminum, gallium, and indium; providing a getter ata level of at least 100 ppm with respect to the source material into thechamber such that the getter contacts the source material; transferringa nitrogen-containing material into the chamber; heating the chamber toa determined temperature; pressurizing the chamber to a determinedpressure; processing the nitrogen-containing material with the sourcematerial in the chamber to form a polycrystalline gallium-containinggroup III metal nitride comprising a plurality of grains of acrystalline gallium-containing group III metal nitride; the plurality ofgrains having an average grain size in a range from about 10 nanometersto about 10 millimeters and defining a plurality of grain boundaries;and the polycrystalline gallium-containing group III metal nitridematerial having: an atomic fraction of a gallium-containing group IIImetal in a range from about 0.49 to about 0.55, the gallium-containinggroup III metal being selected from at least one of aluminum, indium,and gallium; and an oxygen content in the form of a gallium-containinggroup III metal oxide or a substitutional impurity within thepolycrystalline gallium-containing group III metal nitride less thanabout 10 parts per million (ppm); and a plurality of inclusions withinat least one of the plurality of grain boundaries and the plurality ofgrains, the plurality of inclusions comprising a getter, the getterconstituting a distinct phase from the crystalline gallium-containinggroup III metal nitride and located within individual grains of thecrystalline gallium-containing group III metal nitride and/or at thegrain boundaries of the crystalline gallium-containing group III metalnitride and being incorporated into the polycrystallinegallium-containing group III metal nitride at a level greater than about200 parts per million, and; forming a crystalline gallium-containinggroup III metal nitride crystal from the polycrystallinegallium-containing group III metal nitride characterized by a wurtzitestructure substantially free from any cubic entities and an opticalabsorption coefficient less than or equal to about 2 cm⁻¹ at wavelengthsbetween about 405 nanometers and about 750 nanometers.

Benefits are achieved over pre-existing techniques using the presentdisclosure. In particular, the present disclosure enables acost-effective manufacture of crystals that serve as a starting materialfor high quality gallium nitride containing crystal growth. In aspecific embodiment, the present method and apparatus can operate withcomponents that are relatively simple and cost effective to manufacture,such as ceramic and steel tubes. A specific embodiment also takesadvantage of a getter material suitable for processing one or morechemicals for manufacture of high quality gallium nitride startingmaterial. Depending upon the embodiment, the present apparatus andmethod can be manufactured using conventional materials and/or methodsaccording to one of ordinary skill in the art. In specific embodiments,the final crystal structure is substantially clear and free of haze andother features that may be undesirable. Depending upon the embodiment,one or more of these benefits may be achieved. These and other benefitsmay be described throughout the present specification and moreparticularly below.

The present disclosure achieves these benefits and others in the contextof known process technology. However, a further understanding of thenature and advantages implementing embodiments according to the presentdisclosure may be realized by reference to the latter portions of thespecification and attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1, 2, and 3 are schematic diagrams illustrating reactors accordingto embodiments of the present disclosure;

FIG. 4 is a simplified flow diagram of a synthesis method according toan embodiment;

FIG. 5 is a simplified flow diagram of utilization method according toan embodiment; and

FIG. 6 is a simplified system diagram according to an embodiment.

DETAILED DESCRIPTION

According to the present disclosure, techniques related to processing ofmaterials for growth of crystals are provided. More particularly, thepresent disclosure provides a crystalline nitride material suitable foruse as a raw material for crystal growth of a gallium-containing nitridecrystal by an ammonothermal technique, including ammonobasic orammonoacidic technique, but there can be others. In other embodiments,the present disclosure provides methods suitable for synthesis ofpolycrystalline nitride materials, but it would be recognized that othercrystals and materials can also be processed, including single crystalmaterials. Such crystals and materials include, but are not limited to,GaN, AN, InN, InGaN, AlGaN, and AlInGaN, and others for manufacture ofbulk or patterned substrates. Such bulk or patterned substrates can beused for a variety of applications including optoelectronic devices,lasers, light emitting diodes, solar cells, photoelectrochemical watersplitting and hydrogen generation, photodetectors, integrated circuits,and transistors, among other devices.

The disclosure discusses embodiments that may relate to a crystallinecomposition. The disclosure includes embodiments that may relate to anapparatus for making a crystalline composition. The disclosure includesembodiments that may relate to a method of making and/or using thecrystalline composition.

Approximating language, as used herein throughout the specification andclaims, may be applied to modify any quantitative representation thatcould permissibly vary without resulting in a change in the basicfunction to which it may be related. Accordingly, a value modified by aterm such as “about” may not be limited to the precise value specified.In at least one instance, the variance indicated by the term about maybe determined with reference to the precision of the measuringinstrumentation. Similarly, “free” may be combined with a term; and, mayinclude an insubstantial number, or a trace amount, while still beingconsidered free of the modified term unless explicitly stated otherwise.

According to one embodiment according to the present disclosure, acomposition of a polycrystalline metal nitride is provided. Thepolycrystalline metal nitride may have a plurality of grains, and thesegrains may have a columnar structure. In some embodiments, many grainsmay be bonded or adhered to one another, forming a polycrystallineplate. In other embodiments, a smaller number of grains may be bonded oradhered to one another, forming a polycrystalline powder.

With reference to the grains, the grains may be characterized by one ormore properties. The properties may include a grain dimension. Otherproperties may include an average number of grains per unit volume, aninter-grain bend strength or a tilt angle of the grains relative to eachother.

The grain dimension may refer to either an average grain size or anaverage grain diameter. The grains may have a columnar structure; inthis case they have a major axis, and the average grain size refers toan average length of the grains along the major axis. Perpendicular tothe major axis may be one or more minor axes, and the average diameterof each grain may be determined with reference to the minor axes.Collectively, the average diameters of each of the grains may beaggregated and averaged to provide the average grain diameter. Anaverage, as used herein, may refer to the mean value.

The average grain size of the polycrystalline metal nitride may be in arange of greater than about 10 nanometers. In one embodiment, theaverage grain size may be in a range of from about 0.01 micrometer toabout 10 millimeters, while in certain other embodiments, the grain sizemay be in a range of from about 0.01 micrometer to about 30 micrometers,from about 30 micrometers to about 50 micrometers, from about 50micrometers to about 100 micrometers, from about 100 micrometers toabout 500 micrometers, from about 500 micrometers to about 1 millimeter,from about 1 millimeter to about 3 millimeters, from about 3 millimetersto about 10 millimeters or greater than about 10 millimeters. Theaverage grain diameter may be larger than about 10 micrometers. In oneembodiment, the average grain diameter may be in a range of from about10 micrometers to about 20 micrometer, from about 20 micrometers toabout 30 micrometers, from about 30 micrometers to about 50 micrometers,from about 50 micrometers to about 100 micrometers, from about 100micrometers to about 500 micrometers, from about 500 micrometers toabout 1 millimeter, from about 1 millimeter to about 3 millimeters, fromabout 3 millimeters to about 10 millimeters or greater than about 10millimeters.

An average number of grains per unit volume of the crystallinecomposition may indicate a grain average or granularity. The compositionmay have an average number of grains per unit volume of greater thanabout 100 per cubic centimeter. In one embodiment, the average number ofgrains per unit volume may be in a range of from about 100 per cubiccentimeter to about 1000 per cubic centimeter, from about 1000 per cubiccentimeter to about 10,000 per cubic centimeter, from about 10,000 percubic centimeter to about 10⁵ per cubic centimeter, or greater thanabout 10⁵ per cubic centimeter.

The grains may be oriented at a determined angle relative to each other.The orientation may be referred to as the tilt angle, which may begreater than about 1 degree. In one embodiment, the grain orientation ortilt angle may be in a range of from about 1 degree to about 3 degrees,from about 3 degrees to about 5 degrees, from about 5 degrees to about10 degrees, from about 10 degrees to about 15 degrees, from about 15degrees to about 30 degrees, or greater than about 30 degrees.

Properties that are inherent in or particular to one or more crystallinearticles produced according to an embodiment of the present disclosuremay include bend strength, density, moisture resistance, and porosity,among others. The properties may be measured using the correspondingASTM standard test. Example of the ASTM standard test may include ASTMC1499.

The inter-grain bend strength of a film comprising one or more ofcrystals may be greater than about 20 MegaPascal (MPa). In oneembodiment, the inter-grain bend strength may be in a range of fromabout 20 MegaPascal to about 50 MegaPascal, from about 50 MegaPascal toabout 60 MegaPascal, from about 60 MegaPascal to about 70 MegaPascal,from about 70 MegaPascal to about 75 MegaPascal, from about 75MegaPascal to about 80 MegaPascal, from about 80 MegaPascal to about 90MegaPascal, or greater than about 90 MegaPascal. The bend strength mayindicate the grain to grain relationship at the inter-grain interfaceand/or the inter-grain strength.

The apparent density of crystalline articles may be greater than about 1gram per cubic centimeter (g/cc). In one embodiment, the density may bein a range of from about 1 gram per cubic centimeter to about 1.5 gramsper cubic centimeter, from about 1.5 grams per cubic centimeter to about2 grams per cubic centimeter, from about 2 grams per cubic centimeter toabout 2.5 grams per cubic centimeter, from about 2.5 grams per cubiccentimeter to about 3 grams per cubic centimeter, greater than about 4grams per cubic centimeter, greater than about 5 grams per cubiccentimeter, or greater than about 6 grams per cubic centimeter. Thecrystalline composition density may be a function of, for example, theporosity or lack thereof, the crystal packing arrangement, and the like.

The crystalline article may be aluminum nitride and may have an apparentdensity of less than about 3.26 gram per cubic centimeter at standardtest conditions. In one embodiment, the aluminum nitride crystallinearticle may have an apparent density in a range of from about 3.26 gramper cubic centimeter to about 2.93 gram per cubic centimeter, from about2.93 gram per cubic centimeter to about 2.88 gram per cubic centimeter,from about 2.88 gram per cubic centimeter to about 2.5 gram per cubiccentimeter, from about 2.5 gram per cubic centimeter to about 1.96 gramper cubic centimeter, or less than about 1.96 gram per cubic centimeter.

The crystalline article may be gallium nitride and may have an apparentdensity of less than about 6.2 gram per cubic centimeter at standardtest conditions. In one embodiment, the gallium nitride crystallinearticle may have an apparent density in a range of from about 6.2 gramper cubic centimeter to about 5.49 gram per cubic centimeter, from about5.49 gram per cubic centimeter to about 4.88 gram per cubic centimeter,from about 4.88 gram per cubic centimeter to about 4.27 gram per cubiccentimeter, from about 4.27 gram per cubic centimeter to about 4 gramper cubic centimeter, or less than about 4 gram per cubic centimeter.

The porosity of the polycrystalline composition may be in a range ofless than about 30 percent by volume. In one embodiment, the porositymay be in a range of from about 30 percent to about 10 percent, fromabout 10 percent to about 5 percent, from about 5 percent to about 1percent, from about 1 percent to about 0.1 percent, or less than about0.1 percent by volume.

The metal of the metal nitride may include a group III metal. Suitablemetals may include one or more of aluminum, gallium, or indium. The “oneor more” refers to combination of metals in the metal nitride, and mayinclude compositions such as aluminum gallium nitride (AlGaN), indiumgallium nitride (InGaN), aluminum indium nitride (AlInN), aluminumindium gallium nitride (AlInGaN), and the like.

A fraction of the metal, or metals, in the metal nitride may be selectedsuch that there is no excess metal in the metal nitride. In oneembodiment, the atomic fraction of the metal may be greater than about49 percent. In another embodiment, the atomic fraction may be in a rangeof from about 49 percent to about 50 percent, from about 50 percent toabout 51 percent, from about 51 percent to about 53 percent, from about53 percent to about 55 percent, or greater than about 55 percent.

In some embodiments, the group III metal nitride comprises a powder. Theparticle size of the powder may be between about 0.1 micron and about100 microns. Some powder particles may comprise single crystals. Somepowder particles may comprise at least two grains. In other embodiments,the group III metal nitride comprises a grit. The particle size of thegrit may be between about 100 microns and about 10 millimeters. Somegrit particles may comprise single crystals. Some grit particles maycomprise at least two grains.

The metal nitride composition may contain one or more impurities. Asused herein, and as is commonly used in the art, the term “impurity”refers to a chemical species that is distinct from the group III metalnitride that constitutes the majority composition of the polycrystallinemetal nitride. Several classes of impurities may be distinguished, withrespect to chemistry, atomic structure, intent, and effect. Impuritieswill generally comprise elements distinct from nitrogen, aluminum,gallium, and indium, including oxygen, carbon, halogens, hydrogen,alkali metals, alkaline earth metals, transition metals, and main blockelements. The impurity may be present in a number of forms, withdifferent atomic structure. In some cases, the impurity is present as anisolated atom or ion within the crystalline lattice of the group IIImetal nitride, for example, as a substitutional or interstitialimpurity. In other cases, the impurity is present in a distinct phase,for example, as an inclusion within an individual group III metalnitride grain or within a grain boundary of the group III metal nitride.The impurity may be deliberately added, to enhance the properties of thegroup III metal nitride in some way, or may be unintentional. Finally,the impurity may or may not have a significant effect on the electrical,optical, crystallographic, chemical, or mechanical properties of thegroup III metal nitride. One skilled in the art will recognize that aninclusion comprising, for example, a getter within a crystal grain isdistinguished from a dopant in that an inclusion is present as adistinct phase. An inclusion as a distinct phase has a differentcrystallographic structure than the crystal lattice in which it isembedded whereas a crystal grain having a dopant dispersed within thecrystalline lattice of the crystal grain will exhibit a singlecrystallographic structure.

As used herein, and as is commonly used in the art, the term “dopant”refers to an impurity that is atomically dispersed within the group IIImetal nitride, for example, as a substitutional or interstitialimpurity, and is typically added intentionally. With regard to dopantsand dopant precursors (collectively “dopants” unless otherwiseindicated), the electrical properties of the group III metal nitridecomposition may be controlled by adding one or more of such dopants tothe above composition during processing. The dopant may also providemagnetic and/or luminescent properties to the group III metal nitridecomposition. Suitable dopants may include one or more of s or p blockelements, transition metal elements, and rare earth elements. Suitable sand p block elements may include, for example, one or more of silicon,germanium, magnesium, or tin. Other suitable dopants may include one ormore of transition group elements. Suitable transition group elementsmay include one or more of, for example, zinc, iron, or cobalt. Suitabledopants may produce an n-type material, a p-type material, or asemi-insulating material. In some embodiments, oxygen, whether addedintentionally or unintentionally, also acts as a dopant.

Suitable dopant concentration levels in the polycrystalline compositionmay be greater than about 10¹⁰ atoms per cubic centimeter. In oneembodiment, the dopant concentration may be in a range of from about10¹⁰ atoms per cubic centimeter to about 10¹⁵ atoms per cubiccentimeter, from about 10¹⁵ atoms per cubic centimeter to about 10¹⁶atoms per cubic centimeter, from about 10¹⁶ atoms per cubic centimeterto about 10¹⁷ atoms per cubic centimeter, from about 10¹⁷ atoms percubic centimeter to about 10¹⁸ atoms per cubic centimeter, from about10¹⁸ atoms per cubic centimeter to about 10²¹ atoms per cubiccentimeter, or greater than about 10²¹ atoms per cubic centimeter.

As used herein, the term “getter” refers to a substance that isintentionally added to a process or a composition to remove or reactwith undesired impurities. The getter has a higher chemical affinity foran undesired impurity, for example, oxygen, than the principal metallicconstituent of the composition, for example, gallium. The getter maybecome incorporated into the polycrystalline group III metal nitride inthe form of an inclusion, for example, as a metal nitride, a metalhalide, a metal oxide, a metal oxyhalide, or as a metal oxynitride.Examples of suitable getters include the alkaline earth metals, boron,carbon, scandium, titanium, vanadium, chromium, yttrium, zirconium,niobium, the rare earth metals (also known as the lanthanides or thelanthanide metals), hafnium, tantalum, and tungsten, and their nitrides,oxynitrides, oxyhalides, and halides. In some embodiments, an elementalcomposition or substance can act as either a getter or as a dopant, suchas magnesium. In other cases, the getter impurity atom has a largeratomic or covalent diameter than gallium and does not becomeincorporated as a dopant at sufficient levels to modify the electricalproperties of the group III metal nitride significantly, and thereforefunctions predominantly or exclusively as a getter. The getter may bepresent in the polycrystalline group III metal nitride as a distinctphase, within individual grains of a crystalline group III metal nitrideand/or at grain boundaries of a crystalline group III metal nitride, ata level greater than 100 ppm, from about 100 ppm to about 200 ppm, fromabout 200 ppm to about 500 ppm, from about 500 ppm to about 0.1%, fromabout 0.1% to about 0.2%, from about 0.2% to about 0.5%, from about 0.5%to about 2%, from about 2% to about 10%, or greater than 10%. Parts permillion (ppm) and “%” refer to “by weight” unless otherwise indicated.

In other cases, impurities are unintended and/or undesirable inclusionsin the polycrystalline group III metal nitride, and may result from, forexample, processing and handling. Other unintentional impurities mayresult from contaminants in raw materials. Some unintentional impuritiesmay be more closely associated with select raw materials. In someembodiments, the unintentional impurity includes oxygen present as asubstitutional impurity, or dopant, in the polycrystalline group IIImetal nitride at higher than the desired level. In other embodiments,the unintentional impurity includes oxygen present as a group III oxideinclusion, for example, Ga₂O₃, Al₂O₃, and/or In₂O₃. The unintentionaloxygen impurity may originate from residual oxygen in the metal rawmaterial, from moisture or O₂ present as an impurity in the gaseous rawmaterials used in the synthesis process, from moisture or O₂ generatedfrom outgassing of the reactor components during the synthesis process,from reaction of the gaseous raw materials with one or more of thereactor materials during the synthesis process, or from an air leak inthe reactor. In one embodiment, the oxygen content present as Ga₂O₃ oras a substitutional impurity within the polycrystalline group III metalnitride may be less than about 10 parts per million (ppm). In anotherembodiment, the oxygen content present as Ga₂O₃ or as a substitutionalimpurity within the polycrystalline gallium nitride may be in a range offrom about 10 parts per million to about 3 parts per million, from about3 parts per million to about 1 part per million, from about 1 part permillion to about 0.3 parts per million, from about 0.3 part per millionto about 0.1 parts per million, or less than about 0.1 part per million.

Getters are often used to purify the gases being used to synthesizepolycrystalline gallium-containing group III nitride materials. Howeverin these uses, the incorporation of the getter into the polycrystallinematerial is avoided. In contrast, it is an object of the invention todeliberately incorporate a getter phase into the polycrystalline groupIII nitride materials so formed. In some embodiments according to thepresent disclosure, a getter material is provided in a crucible alongwith a group III metal. In other embodiments, a getter material isprovided to a chamber in which a group III metal or a group III metalhalide is to be processed. In some embodiments according to the presentdisclosure, a getter material is provided in a separate crucible orsource from the group III metal crucible and transported to a cruciblewhere a group III metal is to be processed. In some embodiments, agetter material is provided in a separate crucible or source from thegroup III metal and transported to a region wherein a polycrystallinegroup III nitride material is formed. In some embodiments, the gettermaterial, or a distinct phase comprising at least one component of thegetter material, is incorporated into the polycrystalline group IIImetal nitride as an inclusion within or between grains of crystallinegroup III metal nitride. In other embodiments, the getter removesimpurities from the growth environment in the gas phase and does notbecome incorporated into the polycrystalline group III metal nitride. Insome embodiments, the getter removes impurities from the growthenvironment by forming a solid compound that does not becomeincorporated into the polycrystalline group III metal nitride.

Referring now to the apparatus that includes an embodiment according tothe present disclosure, the apparatus may include sub systems, such as ahousing, one or more supply sources, and a control system.

The housing may include one or more walls, components, and the like. Thewalls of the housing may be made of at least one of a metal, arefractory material, or a metal oxide. In one embodiment, the walls ofthe housing comprise at least one of fused silica, alumina, carbon,iron-based alloy, chromium-based alloy, molybdenum, molybdenum-basedalloy, or boron nitride. In one embodiment, the housing may have aninner wall, and an outer wall spaced from the inner wall. An innersurface of the inner wall may define a chamber.

The walls of the housing may be configured (e.g., shaped or sized) withreference to processing conditions and the desired end use. Theconfiguration may depend on the size and number of components, and therelative positioning of those components, in the chamber. The chambermay have a pre-determined volume. In one embodiment, the housing may bea rectangular cuboid. In one embodiment, the housing may be cylindricalwith an outer diameter in a range of from about 5 centimeters to about 1meter, and a length of from about 20 centimeters to about 10 meters. Thehousing may be elongated horizontally, or vertically. The orientation ofthe elongation may affect one or more processing parameters. For exampleand as discussed in further detail below, for a horizontal arrangement,a series of crucibles may be arranged in a series such that a stream ofreactants flow over the crucibles one after another. In such anarrangement, the concentration and composition of the reactant streammay differ at the first crucible in the series relative to the lastcrucible in the series. Of course, such an issue may be addressed withsuch configuration changes as rearrangement of the crucibles,redirection of the reactant stream(s), multiple reactant stream inlets,and the like.

A liner may be disposed on the inner surface of the inner wall along theperiphery of the chamber. Suitable liner material may include graphite,boron nitride, metal, or graphite coated with a material such as TaC,SiC or pyrolytic boron nitride. The liner and other inner surfaces maynot be a source of undesirable contaminants. The liner may prevent orreduce material deposition on the inner surface of the inner wall. Theliner may prevent or reduce etching of the walls of the housing byhalides of getter metals. Failing the prevention of material deposition,the liner may be removable so as to allow the deposited material to bestripped from the inner wall during a cleaning process and/orreplacement of the liner. In another embodiment, the housing may containan outer wall and an inner wall, and the inner wall may comprisegraphite, boron nitride, metal, or graphite coated with a material suchas TaC, SiC or pyrolytic boron nitride and may possess one or more ofthe benefits described above for the liner.

Because the inner wall may be concentric to and spaced from the outerwall, the space may define a pathway between the inner wall and theouter wall for environmental control fluid to flow therethrough.Suitable environmental control fluids that may be used for circulationmay include inert gases. Environmental control fluid may include gas,liquid or supercritical fluid. An environmental control inlet may extendthrough the outer wall to the space. A valve may block the environmentalcontrol fluid from flowing through the inlet and into the pathway tocirculate between the inner and outer walls. In one embodiment, theinlet may be part of a circulation system, which may heat and/or coolthe environmental control fluid and may provide a motive force for thefluid. The circulation system may communicate with, and respond to, thecontrol system. Flanges, such as those meant for use in vacuum systems,may provide a leak proof connection for the inlet.

Suitable components of the housing may include, for example, one or moreinlets (such as raw material inlets, gas inlets, carrier gas inlets, anddopant inlets), one or more outlets, filters, heating elements, coldwalls, hot walls, pressure responsive structures, crucibles, baffles,and sensors. Some of the components may couple to one or more of thewalls, and some may extend through the walls to communicate with thechamber, even while the housing is otherwise sealed. The inlets and theoutlet may further include valves.

The inlets and the outlet may be made from one or more materialssuitable for semiconductor manufacturing, such as electro-polishedstainless steel materials, corrosion-resistant metal alloys (such asHastelloy™), quartz, or refractory materials. The inlets and/or outletsmay be welded or fused to the respective wall, or may be secured to thewall by one or more metal-to-metal, quartz-to-quartz, or metal-to-quartzseals. The inlets may extend into a hot zone in the chamber.Accordingly, the inlets may be composed of multiple materials whereindifferent materials are used in different regions of the reactor (orchamber). Different inlet materials may be chosen based on thetemperature of the region and the chemical exposure. In one embodiment,a hot zone of the chamber may have inlets that comprise graphite,molybdenum, tungsten, or rhenium or one or more of an oxide, a nitride,or an oxynitride of silicon, aluminum, magnesium, boron, or zirconium.In a specific embodiment, the one or more inlets in a hot zone maycomprise a non-oxide material, such as boron nitride, silicon carbide,tantalum carbide, or a carbon material such as graphite. Optionally, theinlets and/or outlets may include purifiers. In one embodiment, thepurifier includes a getter material that does not become incorporatedinto the inlet gas stream, for example a zirconium alloy which may reactwith contaminants in the inlet gas stream to form non-volatile nitrides,oxides and carbides, thus reducing the probability of contamination inthe final product. In one embodiment, the purifiers may be placed in theinlets at the entrance to the chamber. For reactions utilizing largequantities of ammonia the main concern for contamination may be thepresence of water due to hygroscopic nature of ammonia. Thecontamination of ammonia drawn from an ammonia tank may increaseexponentially as the ammonia tank empties and when 70 percent of ammoniais reached, the tank may be replaced. Alternatively, a point-of-usepurifier may be utilized at the inlets. The use of a point-of-usepurifier may help in controlling the contamination in ammonia therebyreducing ammonia wastage. Optionally, lower grade ammonia may beutilized along with the point-of-use purifier to obtain a grade of about99.9999 percent.

The shape or structure of the one or more inlets and outlets may bemodified to affect and control the flow of fluid therethrough. Forexample, an inner surface of the inlet/outlet may be rifled. The riflingmay spin the gas flowing out through the ends and enhance mixing. In oneembodiment, the inlets may be coupled together such that the reactantsmay pre-mix before they reach a reaction zone or a hot zone. Each of theinlets and outlets may have an inner surface that defines an aperturethrough which material can flow into, or out of, the chamber. Valveapertures may be adjustable from fully open to fully closed therebyallowing control of the fluid flow through the inlets and the outlets.

The inlet(s) may be configured to promote mixing of thenitrogen-containing gas and the halide-containing gas upstream of thecrucible(s), so as to promote uniform process conditions throughout thevolume of the chamber. One or more of the inlets may contain one or moreof baffles, apertures, fits, and the like, in order to promote mixing.The apertures, frits, and baffles may be placed within the chamberproximate to the hot zone or crucibles so as to control the flow of gasin the chamber, which may prevent or minimize the formation of solidammonium halide. The apertures, frits, and baffles may be placedupstream of the nearest crucible, with a distance of separation that isin a range from about 2 cm to about 100 cm, in order for mixing to becomplete prior to the onset of reaction with the contents of thecrucible. The presence of apertures and baffles may promote higher gasvelocities that promote mixing and inhibit back-flow of gases,preventing or minimizing the formation of solid ammonium halide.Furthermore, the inlet(s) may be configured to extend into a hot zone ora reaction zone.

One or more crucibles may be placed within the chamber. In oneembodiment, the number of crucibles within the chamber is about 6.Depending on the configuration of the chamber, the crucibles may bearranged horizontally and/or vertically within the chamber. The crucibleshape and size may be pre-determined based on the end usage of the metalnitride, the raw material types, and the processing conditions. For thepolycrystalline composition to be useful as a sputter target, the sizeof the crucible may be relatively larger than the required size of thesputter target. The excess of the polycrystalline composition may beremoved, for example, through etching or cutting to form the sputtertarget article. Such removal may eliminate surface contaminationresulting from contact with the crucible material.

The crucible may withstand temperatures in excess of the temperaturerequired for crystalline composition formation while maintainingstructural integrity, and chemical inertness. Such temperatures may begreater than about 200 degree Celsius, in a range of from about 200degree Celsius to about 1300 degree Celsius, or greater than about 1300degrees Celsius. Accordingly, refractory materials may be suitable foruse in the crucible. In one embodiment, the crucible may include arefractory composition including an oxide, a nitride, or an oxynitride.The crucible may be formed from one or more of graphite, molybdenum,tungsten, or rhenium or from one or more of an oxide, a nitride, or anoxynitride of silicon, aluminum, magnesium, boron, or zirconium. In aspecific embodiment, the crucible comprises a non-oxide material, suchas boron nitride, silicon carbide, tantalum carbide, or a carbonmaterial such as graphite. In one embodiment, a removable liner may beplaced inside the crucible so as to facilitate easy removal of a rawmaterial and/orpolycrystalline composition. The removable liner may beformed of graphite or boron nitride. In some embodiments, a getter isadded to the crucible in the form of a foil or liner. In one specificembodiment, the getter foil or liner is chosen from at least one ofzirconium, hathium, and tantalum. In another embodiment, the cruciblecomposition comprises at least one getter.

A quantity of group III metal, comprising at least one of aluminum,gallium, and indium, may be placed in at least one crucible. The groupIII metal may be added in solid or liquid form. A getter, comprising atleast one of the alkaline earth metals, boron, carbon, scandium,titanium, vanadium, chromium, yttrium, zirconium, niobium, the rareearth metals, hafnium, tantalum, and tungsten, may also be placed in theat least one crucible along with the group III metal. In anotherembodiment, a getter, comprising at least one of the alkaline earthmetals, boron, carbon, scandium, titanium, vanadium, chromium, yttrium,zirconium, niobium, the rare earth metals, hafnium, tantalum, andtungsten, may be placed in one more separate crucibles that optionallydo not contain a group III metal. The getter may be added at a levelgreater than 100 ppm, greater than 300 ppm, greater than 0.1%, greaterthan 0.3%, greater than 1%, greater than 3%, or greater than 10% byweight with respect to the group III metal within the chamber. Thegetter may be added in the form of a solid, including as a powder, grit,pellet, wire, or foil. The getter may be added in the form of a metal, anitride, a halide, or a mixture or compound thereof. The getter maycontain oxygen. In another embodiment, the group III metal, comprisingat least one of aluminum, gallium, and indium, may be introduced intothe chamber in a gaseous form, for example, in the form of a metalhalide.

In one embodiment, at least one wetting agent is also added to thecrucible, contacting the group III metal. As used herein, “wettingagent” refers to an element or a compound that facilitates the mixing ofor a reaction between an otherwise immiscible liquid mixture at theinterface of the two components. The wetting agent can be any metal thatfacilitates interfacial wetting of a binary liquid metal mixture anddoes not readily react to form covalent bonds with a Group III element.Any suitable and effective wetting agent compound can be employed.Suitable wetting agents include bismuth (Bi), lead (Pb), germanium (Ge),and tin (Sn). Other suitable wetting agents include antimony (Sb),tellurium (Te), and polonium (Po). The reaction mixture can also includea mixture of two or more wetting agents, in any proportion. The reactionmixture can include a wetting agent compound, such as organometalliccompounds containing the wetting agent metal or inorganic compoundscontaining the wetting agent metal. Suitable wetting agent compoundsinclude, e.g., halides, oxides, hydroxides, and nitrates. Many suitableand effective wetting agents and wetting agent compounds are disclosed,e.g., in Aldrich Handbook of Fine Chemicals, 2003-2004 (Milwaukee,Wis.). As used herein, bismuth, germanium, tin, and lead refer toelemental metals, alloys containing these metals, compounds containingthese metals, and mixtures thereof. The Group III metal and the wettingagent can be present in a molar ratio of about 1:1 to about 500:1.Specifically, the Group III element and the wetting agent can be presentin a molar ratio of about 2:1, about 5:1, about 20:1, about 100: 1, orabout 200:1.

In certain embodiments, a group III metal is provided to the chamber inthe form of a halide, for example, as one or more of GaCl₃, GaCl, AlCl₃,or InCl₃. The group III metal halide may be generated by passing ahalogen-containing gas, for example, hydrogen chloride or chlorine, overa crucible containing at least one group III metal and placed within asecond chamber which is placed upstream of the chamber in which thepolycrystalline group III metal nitride is synthesized.

One or more substrates or surfaces may be placed downstream of acrucible containing a group III metal or of an inlet from which a groupIII metal halide is provided, that is, between the group III metalsource and the outlet of the chamber. The one or more substrates orsurfaces may be formed from one or more of graphite, molybdenum,tungsten, or rhenium or from one or more of an oxide, a nitride, or anoxynitride of silicon, aluminum, magnesium, boron, or zirconium. In aspecific embodiment, the one or more substrates or surfaces comprises anon-oxide material, such as boron nitride, silicon carbide, tantalumcarbide, or a carbon material such as graphite. The substrates orsurfaces may comprise flat disks, rods, tubes, cones, annular segments,conical sections, crucibles, or the like. The one or more substrates orsurfaces may serve as a location for formation of a polycrystallinegroup III metal nitride. In one embodiment, the substrates or surfacesmay further contain polycrystalline group III nitride which may serve asa location or seed for growth during the growth process, for example, inthe form of a powder, a film, or adherent particles.

Suitable sensors may include one or more of pressure sensors,temperature sensors, and gas composition sensors. The sensors may beplaced within the chamber, within the outlet(s), and/or within theinlet(s), and may communicate the process parameters in the chamber tothe control system.

Suitable supply sources may include one or more of an energy source, anitrogen-containing gas source, a carrier gas source, a getter gassource, a halide-containing gas source, a raw material source (sometimesreferred to as a reservoir), a dopant gas source, environmental controlfluid source, and the like.

The energy source may be located proximate to the housing and may supplyenergy, such as thermal energy, plasma energy, or ionizing energy to thechamber through the walls. The energy source may be present in additionto, or in place of, the heating elements disclosed above. In oneembodiment, the energy source may extend along an outward facing surfaceof the outer wall of the housing. The energy source may provide energyto the chamber. In one embodiment, the energy source may be within thehousing and supply energy, such as thermal energy, plasma energy, orionizing energy to the crucible(s) and reaction region. The energysource may be present in addition to, or in place of, the heatingelements disclosed above. In one embodiment, the energy source mayextend above, below, or beside the crucible(s) and reaction region. Theenergy source may provide energy to the chamber. Multiple energy sourcesmay be applied to supply energy. In one embodiment, the multiple energysources may permit controllable heating of a crucible within the chamberto a particular temperature and heating of a reaction region to adifferent temperature. In one embodiment, two or more crucibles withinthe chamber may be heated to a different temperature.

The energy source may be a microwave energy source, a thermal energysource, a plasma source, or a laser source. In one embodiment, thethermal energy may be provided by a heater. Suitable heaters may includeone or more molybdenum heaters, tube furnaces, split furnace heaters,three-zone split furnaces, graphite heaters, or induction heaters.

Sensors may be placed within the chamber. The sensors may be capable ofwithstanding high temperature and elevated or reduced pressure in thechamber and may be chemically inert. The sensors may be placed proximateto the crucible, and/or may be placed at the inlet(s), outlet(s), oranother location within the housing. The sensors may monitor processconditions such as the temperature, pressure, gas composition andconcentration within the chamber.

The nitrogen-containing gas source may communicate through a first inletwith the chamber. The nitrogen-containing gas source may include one ormore filters, purifiers, or driers to purify and/or dry thenitrogen-containing gas. In one embodiment, the nitrogen-containing gasmay be produced at the source. The purifier may be able to maintainpurity levels of the nitrogen-containing gas up to or abovesemiconductor grade standards for purity. Suitable nitrogen-containinggases may include ammonia, diatomic nitrogen, and the like. Where thepresence of carbon is not problematic, nitrogen-containing organics maybe used.

Controlling the aperture of the associated valve allows control of theflow rate of the nitrogen-containing gas into the chamber. Unlessotherwise specified, flow rate will refer to volumetric flow rate.Processing considerations, sample size, and the like may determine anappropriate flow rate of the gas. The flow rate of nitrogen-containinggas may be greater than about 10 (standard) cubic centimeters perminute. In one embodiment, the flow rate of nitrogen-containing gas maybe in a range of from about 10 cubic centimeters per minute to about 100cubic centimeters per minute, from about 100 cubic centimeters perminute to about 200 cubic centimeters per minute, from about 200 cubiccentimeters per minute to about 500 cubic centimeters per minute, fromabout 500 cubic centimeters per minute to about 1200 cubic centimetersper minute, from about 1200 cubic centimeters per minute to about 2000cubic centimeters per minute, from about 2000 cubic centimeters perminute to about 3000 cubic centimeters per minute, from about 3000 cubiccentimeters per minute to about 4000 cubic centimeters per minute, fromabout 4000 cubic centimeters per minute to about 5000 cubic centimetersper minute, from about 5 standard liters per minute to about 10 standardliters per minute, from about 10 standard liters per minute to about 20standard liters per minute, from about 20 standard liters per minute toabout 50 standard liters per minute, or greater than about 50 standardliters per minute. In some embodiments, the flow of thenitrogen-containing gas in units of volume per second is chosen to begreater than 1.5 times the volume of the group III metal. In someembodiments, the flow of the nitrogen-containing gas is supplied at agas flow velocity of at least 0.1 centimeters per second on the surfaceof the group III metal, at a reaction temperature of at least 700degrees Celsius and no greater than 1300 degrees Celsius. In someembodiments, the flow of the nitrogen-containing gas is supplied at agas flow velocity of at least 0.1 centimeters per second and combineswith a gaseous source of the group III metal, for example GaCl, at areaction temperature of at least 700 degrees Celsius and no greater than1,300 degrees Celsius.

The carrier gas source may communicate with the chamber through aninlet, and/or may share the first inlet with the nitrogen-containinggas. Pre-mixing the nitrogen-containing gas with at least one carriergas may dilute the nitrogen-containing gas to a determined level.Because the nitrogen-containing gas may be diluted with a carrier gas,which may be inert, the likelihood of formation of certain halide solidsproximate to the first inlet in the chamber may be reduced. The dilutionof the nitrogen-containing gas with a carrier gas may also serve toachieve a desired gas velocity through an inlet or an orifice or tube.Suitable carrier gases may include one or more of argon, helium,nitrogen, hydrogen, or other inert gases. In one embodiment, the carriergas inlet is positioned so that a stream of carrier gas may impinge on astream of nitrogen-containing gas exiting the first inlet. Dopants maybe entrained in the carrier gas, in one embodiment, for inclusion in thepolycrystalline composition.

A halide-containing gas source may communicate through a second inletwith the chamber. As with the nitrogen-containing gas source, thehalide-containing gas source may include one or more filters, purifiers,driers, and the like, so that the halide-containing gas be purifiedand/or dried at the source. The halide-containing gas may be produced atthe source. Suitable halide-containing gases may include hydrogenchloride, chlorine gas, and the like. In some embodiments, thehalide-containing gas is omitted from the process.

Controlling the aperture of the associated valve allows control of theflow rate of the halide-containing gas into the chamber. Processingconsiderations, sample size, and the like, may determine an appropriateflow rate of the gas. The flow rate of halide-containing gas may begreater than about 10 (standard) cubic centimeters per minute. In oneembodiment, the flow rate of halide-containing gas may be in a range offrom about 10 cubic centimeters per minute to about 50 cubic centimetersper minute, from about 50 cubic centimeters per minute to about 100cubic centimeters per minute, from about 100 cubic centimeters perminute to about 250 cubic centimeters per minute, from about 250 cubiccentimeters per minute to about 500 cubic centimeters per minute, fromabout 500 cubic centimeters per minute to about 600 cubic centimetersper minute, from about 600 cubic centimeters per minute to about 750cubic centimeters per minute, from about 750 cubic centimeters perminute to about 1000 cubic centimeters per minute, from about 1000 cubiccentimeters per minute to about 1200 cubic centimeters per minute, orgreater than about 1200 cubic centimeters per minute.

The halide-containing gas may flow into the chamber from thehalide-containing gas source through a second inlet. As with thenitrogen-containing gas, the halide-containing gas may be pre-mixed withat least one carrier gas to dilute the halide-containing gas to adetermined level. The dilution of the halide-containing gas with aninert, carrier gas may reduce the likelihood of formation of certainhalide solids in the second inlet, proximate to the chamber. Such aformation might reduce or block the flow therethrough. The dilution ofthe halide-containing gas with an inert, carrier gas may also serve toachieve a desired gas velocity through a second inlet, orifice, or tube.Optionally, the carrier gas inlet may be positioned such that a streamof carrier gas may impinge on a stream of halide-containing gas exitinga second inlet or entering the chamber. In one embodiment, dopants maybe entrained in the carrier gas for inclusion in the polycrystallinecomposition.

The halide-containing gas and the nitrogen-containing gas may beintroduced into the chamber in a manner that determines properties ofthe polycrystalline composition. The manner may include simultaneousintroduction at a full flow rate of each component fluid (gas, liquid,or supercritical fluid). Other suitable introduction manners may includepulsing one or more of the components, varying the concentration and/orflow rate of one or more components, or staggered introductions, forexample, to purge the chamber with carrier gas.

The halide-containing gas and the nitrogen-containing gas inlets may bedisposed such that the exit end is located in the hot zone in thechamber. In one embodiment, one or more inlets are located in a regionof the chamber that, during use, has a temperature of greater than about250 degree Celsius at 1 atmosphere, or a temperature in a range of fromabout 250 degree Celsius to about 370 degree Celsius, or greater thanabout 370 degrees Celsius.

The ratio of flow rate of the nitrogen-containing gas to the flow rateof the halide-containing gas may be adjusted to optimize the reaction.In one embodiment, the ratio of flow rate of the nitrogen-containing gasto the flow rate of halide-containing gas may be in a range of greaterthan 30:1, from about 30:1 to about 15:1, from about 15:1 to about 1:1,from about 1:1 to about 1:10, or from about 1:10 to about 1:15.

In certain embodiments, a getter is provided to the chamber in the vaporphase. In a specific embodiment, a metal is provided in an inlet for ahalide-containing gas in a region that has an elevated temperature underoperating conditions. In one embodiment, the metal may react with thehalide-containing gas to form a volatile metal halide, which istransported into the chamber and contacts the group III metal. Inanother embodiment, the metal may reside in the chamber and react with ahalide-containing gas to form a volatile metal halide, which istransported to another part of the chamber. In one embodiment, the metalhalide is transported to the reaction zone where it combines with thenitrogen-containing gas and a halide-containing gas that contains agroup III metal source. In another embodiment, the getter is provideddirectly as a compound, for example, as a halide or as a hydride. Incertain embodiments, the chemical species formed by reaction of thegetter with an undesired impurity, for example, oxygen, is volatileunder operating conditions and is carried away out of the chamber. In aspecific embodiment, the getter is selected from one of a hydrocarbon(C_(w)H_(y), where w, y>0), such as methane (CH₄) or acetylene (C₂H₂), ahalocarbon C_(w)X_(z), where w, z>0 and X =F, Cl, Br, or I), such asCCl₄, a halohydrocarbon (C_(w)H_(y)X_(z), where w, y, z>0 and X=F, Cl,Br, or I), such as chloroform (CHCl₃) or methylene chloride (CH₂Cl₂),phosgene (COCl₂), thionyl chloride (SOCl₂), boron trichloride (BCl₃),diborane (B₂H₆), and hydrogen sulfide (H₂S). In certain embodiments, thechemical species formed by reaction of the getter with an undesiredimpurity, for example, oxygen, is non-volatile under operatingconditions and remains at the mixing or contact point, which may be at adifferent region than the polycrystalline composition.

A raw material source may communicate through a raw material inlet andinto the crucible, which is in the chamber. As with the other sources, araw material source may include one or more filters, driers, and/orpurifiers. Particularly with reference to a raw material source, purityof the supplied material may have a disproportionately large impact oreffect on the properties of the final polycrystalline composition. A rawmaterial may be produced just prior to use and may be kept in an inertenvironment to minimize or eliminate contamination associated withatmospheric contact. If, for example, hygroscopic materials are used, ormaterials that readily form oxides, then a raw material may be processedand/or stored such that the raw material does not contact moisture oroxygen. Further, because the raw material can be melted and flowed intothe chamber during processing, in one embodiment, differing materialsmay be used in a continuous process than might be available for userelative to a batch process. At least some of such differences aredisclosed herein below.

Suitable raw materials may include one or more of gallium, indium, oraluminum. In one embodiment, the raw material may have a purity of99.9999 percent or greater. In another embodiment, the purity may begreater than about 99.99999 percent. The raw material may be a gas; aliquid solution, suspension or slurry; or a molten liquid. The residualoxygen in a raw material, particularly a metal, may further be reducedby heating under a reducing atmosphere, such as one containing hydrogen,or under vacuum.

In certain embodiments, one or more crucibles and/or raw materials areloaded into the chamber from a glove box, dry box, desiccator, or otherinert atmosphere environment. In certain embodiments, a polycrystallinegroup III metal nitride is removed from the chamber following asynthesis run directly into a glove box, dry box, desiccator, or otherinert atmosphere environment. For convenience, an inert atmosphere maygenerally be referred to as a glove box for the purposes of thisdocument.

While all of the materials needed for production may be sealed in thechamber during operation in one embodiment; in another embodiment,various materials may be added during the process. For example, a rawmaterial may flow through a raw material inlet, out of an exit end, andinto a crucible within the chamber. Where there is a plurality ofcrucibles, multiple raw material inlets, or one inlet having multipleexit ends, may be used to flow raw material into individual crucibles.In one embodiment, a raw material inlet may be mounted on a linearmotion feed-through structure. Such feed-through structures may allowthe translation of the exit end of a raw material inlet from crucible tocrucible.

The flow and the flow rate of raw material to, and through, a rawmaterial inlet may be controlled by a valve. The valve may be responsiveto control signals from the control system. While the flow rate of a rawmaterial may be determined based on application specific parameters,suitable flow rates may be larger than about 0.1 kilogram per hour. Inone embodiment, the flow rate may be in a range of from about 0.1kilogram per hour to about 1 kilogram per hour, from about 1 kilogramper hour to about 5 kilograms per hour, or greater than about 5kilograms per hour.

A dopant inlet may be in communication with a reservoir containingdopants and the chamber. The reservoir may be made of material compliantto semiconductor grade standards. The reservoir may have provisions topurify/dry the dopants. In one embodiment, the reservoir may haveliners. The liners may prevent corrosion of the reservoir material, orreduce the likelihood of contamination of the dopants by the reservoir.

A dopant source may be separate, or may be co-located with one or moreof the other materials being added during processing. If addedseparately, the dopants may flow directly into a crucible by exiting anend of the dopant inlet. As mentioned, the dopant may be introduced bypre-mixing with, for example, a raw material, a carrier gas, ahalide-containing gas, or a nitrogen-containing gas. Metering of thedopant may control the dopant concentration levels in thepolycrystalline composition. Similarly, the placement of the dopant inthe polycrystalline composition may be obtained by, for example,pulsing, cycling, or timing the addition of the dopant.

Suitable dopants may include dopant precursors. For example, silicon maybe introduced as SiCl₄ SiH₄, or Si₂H₆, and germanium may be introducedas GeCl₄ or GeH₄. Where carbon is a desired dopant, carbon may beintroduced as a hydrocarbon, such as methane, methylene chloride, orcarbon tetrachloride. Suitable dopants may include a halide or ahydride. In situations where carbon is a desired dopant, or aninconsequential contaminant, metals may be introduced as anorganometallic compound. For example, magnesium may be introduced asMg(C₅H₅)₂, zinc as Zn(CH₃)₂, and iron as Fe(C₅H₅)₂. The flow rate ofdopant precursors may be greater than about 10 (standard) cubiccentimeters per minute. In one embodiment, the flow rate of the dopantprecursors may be in a range of from about 10 cubic centimeters perminute to about 100 cubic centimeters per minute, from about 100 cubiccentimeters per minute to about 500 cubic centimeters per minute, fromabout 500 cubic centimeters per minute to about 750 cubic centimetersper minute, from about 750 cubic centimeters per minute to about 1200cubic centimeters per minute, or greater than about 1200 cubiccentimeters per minute. Alternatively, the dopant may be added inelemental form, for example, as an alloy with the raw material or in aseparate crucible. Other suitable dopants may comprise one or more ofSi, O, Ge, Be, Mg, Zn, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Mo, Sn,Ce, Pr, Nd, Pm, Sm, Eu, Dy, Er, Tm, Yb, or Hf.

The one or more outlets, and corresponding valves, may control therelease of material that is inside of the chamber. The released materialmay be vented to atmosphere, or may be captured, for example, to recyclethe material. The released material may be monitored for compositionand/or temperature by an appropriate sensor mounted to the outlet. Thesensor may signal information to the control system. Becausecontamination may be reduced by controlling the flow of material throughthe chamber in one direction, the polycrystalline composition may beremoved from the chamber by an exit structure in the wall at the outletside.

An outlet may be coupled to an evacuation system. The evacuation systemmay be capable of forming a low base pressure or a pressure differentialin the chamber relative to the atmospheric pressure. Suitable basepressure may be lower than about 10⁻⁷ millibar. In one embodiment, thebase pressure may be in a range of from about 10⁻⁷ millibar to about10⁻⁵ millibar, or greater than about 10⁻⁵ millibar. In one embodiment,the pressure differential may be in a range of from about 760 Torr toabout 50 Torr, 50 Torr to about 1 Torr, from about 1 Torr to about 10⁻³Ton, from about 10⁻³ Ton to about 10⁻⁵ Ton, or less than about 10⁻⁵ Ton.The evacuation may be used for pre-cleaning, or may be used duringprocessing.

An outlet may be heated to a temperature, which may be maintained, thatis greater than the temperature where the vapor pressure of an ammoniumhalide that might be formed during processing is greater than theprocess pressure, for example, one bar. By maintaining a temperatureabove the sublimation point of ammonium halide at the reactor pressure,the ammonium halide might flow into a trap or may be precluded fromforming or solidifying near the outlet once formed.

The control system may include a controller, a processor incommunication with the controller, and a wired or wireless communicationsystem that allows the controller to communicate with sensors, valves,sources, monitoring and evaluating equipment, and the like.

The sensors within the chamber may sense conditions within the chamber,such as the temperature, pressure, and/or gas concentration andcomposition, and may signal information to the controller. Flow ratemonitors may signal information about the flow rate through thecorresponding inlet or outlet to the controller. The controller (via theprocessor) may respond to the information received, and may controldevices in response to the information and pre-determined instructionparameters. For example, the controller may signal the energy source toprovide thermal energy to the chamber. The controller may signal one ormore valves to open, close, or open to a determined flow level duringthe course of polycrystalline composition synthesis. The controller maybe programmed to implement a method of growing polycrystallinecompositions.

The resultant polycrystalline composition may be a group III metalnitride. The metal nitride may be doped to obtain one or more of ann-doped or a p-doped composition. The metal nitride may be a metallic,semiconducting, semi-insulating or insulating material. Further, each ofthese compositions may be a magnetic or a luminescent material.

The working of the apparatus and the function of the various componentsare described below with reference to illustrated embodiments. Referringto the drawings, the illustrations describe certain illustrativeembodiments and do not limit the scope of the claims.

An apparatus 100 in accordance with an embodiment is shown in FIG. 1.The apparatus 100 may be used for preparing a metal nitride material,and may include a housing 102 having a wall 104. The wall 104 may havean inner surface 106 that defines a chamber 108. An energy source 110may be located proximate to the wall 104. A first inlet 112 and a secondinlet 114 extend through the wall 104. The inlets 112, 114 defineapertures through which material can flow into, or out of, the chamber108. An outlet 118 extends through the wall 104 to the chamber 108. Acrucible 120 may be disposed in the chamber 108. A liner (not shown) mayline the inner surface 106 of the wall 104.

The energy source 110 may be a thermal energy source, such as a ceramicheater. The inlets 112, 114 and the outlet 118 may be electro-polishedstainless steel suitable for semiconductor grade manufacturing. In aspecific embodiment, the crucible 120 may comprise boron nitride, andthe liner may comprise graphite.

During operation, a group III metal raw material and a getter may befilled into the crucible 120, and the crucible may be pre-loaded intothe chamber. One or more dopants may be placed in the crucible with theraw material. After loading, the crucible 120 may be sealed by a sealingmechanism (not shown).

A nitrogen-containing gas may flow through the first inlet 112 into thechamber 108. The nitrogen-containing gas may include ammonia, and mayinclude a carrier gas for predilution. A halide-containing gas may flowthrough the second inlet 114 and into the chamber 108. Thehalide-containing gas may include hydrogen chloride and/or chlorine. Thehalide-containing gas may be pre-diluted with a carrier gas. Unreactedgases and/or other waste materials may be removed from the chamber 108through the outlet 118. The chamber 108 may be purged by flowing ingases through the inlets 112, 114 and out through the outlet 118 priorto crystalline composition formation. The outflow, optionally, may bemonitored to detect the impurity level of the out-flowing gas, which mayindicate when a sufficient purge has been achieved.

The energy source 110 may be activated. Activating the energy source 110may increase the temperature within the chamber 108 to pre-determinedlevel and at a pre-determined rate of temperature increase. An area,within the chamber 108 and proximate to the crucible 120, may define ahot zone or reaction zone (not shown).

The raw material, already in the crucible 120, may respond to contactwith the nitrogen-containing gas in the presence of thehalide-containing gas, and at the determined temperature, by reacting toform a nitride of the metal, that is, the polycrystalline composition.

We believe that the group III metal reacts with a hydrogen halide orhalogen to form a volatile group III metal halide. The group III metalhalide in turn reacts with the nitrogen-containing gas, for example,ammonia, to form a polycrystalline group III metal nitride. Undertypical processing conditions, most of the group III metal may react toform a polycrystalline group III metal nitride and only a small fractionof the group III metal may be transported away from the crucible in theform of a group III metal halide. Under typical reaction conditions,some, most, or all of the getter may be dissolved in the liquid groupIII metal when the getter is placed within the same crucible as thegroup III metal. Many of the getters disclosed above are broadlymiscible in liquid aluminum, gallium, and indium at temperatures above500-1300 degrees Celsius. Even the refractory metals Zr, Hf, and Ta aresoluble at a level above about 1-2% in gallium at 1300 degrees Celsius.The dissolved getter metal may become well mixed within the molten groupIII metal. The dissolved getter metal may react with dissolved oxygenwithin the molten group III metal, forming an oxide of the getter metal.Like the group III metal, the getter metal may form halides and/ornitrides. At temperatures of about 500 to 1300 degrees Celsius, thegetter metal halides are relatively volatile and the getter metalnitrides, oxides, and oxynitrides are generally not volatile. In thecase of some getters, for example, the alkaline earth metals andyttrium, the halides may be formed predominantly and most of the gettermetal transported away from the crucible. During the reaction andtransport process, however, the getter metal efficiently ties up orremoves oxygen from the group III metal and from sources of oxygen inthe gas phase, including O₂ and H₂O. In the case of other getters, forexample, Cr and Ta, the nitrides may be formed predominantly and most ofthe getter metal may remain in the crucible in the form of nitride,oxynitride, and oxide inclusions within the polycrystalline group IIInitride for processes that involve exposure the of the group III metalcrucible to a nitrogen-containing source. During the reaction andtransport process, the getter metal efficiently ties up or removesoxygen from the group III metal and/or from sources of oxygen in the gasphase.

In some embodiments, including those not involving the addition of ahydrogen halide to the reaction, most or all of the getter may becomeincorporated into the polycrystalline group III nitride composition.

Referring to FIG. 1, after the polycrystalline composition has beenformed, the housing 102 may be opened at an outlet side. Opening on theoutlet side may localize any introduced contaminants to the chamber 108caused by the opening to the chamber side proximate to the outlet 118.Localizing the contaminants proximate to the outlet 118 may reduce thedistance the contaminants must travel to purge from the chamber 108, andmay confine the path of the contaminants to regions in which thecontaminants are less likely to contact any grown crystal, orcrystalline composition growing surface (such as an inner surface of thecrucible 120). In addition, not opening the housing on the inlet sidemay decrease the likelihood of a leak proximate to the inlet during asubsequent run. Thus, such a configuration may reduce the chance ofcontaminants contaminating the produced crystals. In another embodiment,the housing 102 may be opened on an inlet side of the chamber 108. Incertain embodiments, the housing 102 is connected to a glove box and maybe opened without exposing chamber 108 to ambient air.

An apparatus 200 in accordance with an embodiment is shown in FIG. 2.The apparatus 200 may include a housing 202, and an energy source 204proximate to the housing 202. The housing 202 may include an inner wall206 and an outer wall 208. An inlet 209 may extend through the outerwall 208, but may stop short of the inner wall 206. The outer wall 208may have an outward facing surface. An inward facing surface or innersurface 212 of the inner wall 206 may define a chamber 214.

The inner wall 206 may be nested within, and spaced from, the outer wall208. The space between the walls 206 and 208 may be used to circulate anenvironmental control fluid that may enter the space through the inlet209 configured for that purpose. The outer wall 208 may be formed frommetal or quartz, while the inner wall 206 may be made of quartz or fromboron nitride. The energy source 204 may be proximate to the outer wall208.

A first inlet 216, a second inlet 218, a raw material inlet 224, adopant inlet 232, and an outlet 226 may extend through the inner andouter walls 206 and 208. An additional inlet for a vapor phase getter(not shown) may also extend through the inner and outer walls 206 and208. A plurality of valves 215, 220, 223, 233 may be disposed, one pertube, within the feed tubes that extend from sources to thecorresponding inlets 216, 218, 224, and 232. The individual feed tubesare not identified with reference numbers. And, an outlet 226 may have avalve 227 that may allow or block the flow of fluid therethrough.

A first inlet 216 may communicate with a nitrogen-containing gas source217 and flow a nitrogen-containing gas into the chamber 214. Thenitrogen-containing gas may include ammonia. The nitrogen-containing gasmay be diluted with one or more carrier gases. The carrier gas maycomprise argon, helium, hydrogen, or nitrogen, and may be controllableseparately from the nitrogen-containing gas flow. A second inlet 218 maybe in communication with a halide-containing gas source 219. The secondinlet 218 may allow a halide-containing gas to flow from thehalide-containing gas source 219 into the chamber 214. The valve 220 maycontrol the flow of the halide-containing gas from the halide-containinggas source 219 through the second inlet 218 and into the chamber 214.The halide-containing gas may include hydrogen chloride or chlorine,which may have been diluted with a carrier gas. The raw material inlet224 may communicate with a raw material reservoir 222. An exit end ofthe raw material inlet 224 may be positioned so as to flow raw materialleaving the raw material inlet 224 into a crucible 230. The valve 223may control the flow of the raw material from the reservoir 222 throughthe raw material inlet 224 and into the chamber 214. The raw materialmay include molten gallium.

A dopant source (not shown) may communicate with the chamber 214 througha dopant inlet 232. A valve 233 may be switched on/off to open or blocka flow of dopant from the dopant source into the chamber 214. In theillustrated embodiment, the dopant may include silicon, which may be inthe form of SiCl₄, or germanium, which may be in the form of GeCl₄.

An outlet 226 may allow for excess material to exit the chamber 214. Avalve 227 may open or close, and by closing, a back pressure might bebuilt up as additional materials are flowed into the chamber 214 and thetemperature is increased.

A plurality of crucibles 230 may be provided in the chamber 214. Thecrucibles 230 may be arranged horizontally relative to each other and/orvertically. One or more sensors 236 and one or more sensors 237 may beprovided to monitor the pressure and temperature, or other processparameters within the chamber 214.

As disclosed hereinabove, the environmental control fluid may flow inthe space between the walls through the inlet 209. Inlet 209 maycommunicate with a circulation system (not shown) to circulate the fluidin the space between the walls. Inlet 209 may include a valve 211 toadjust or optimize the circulation in the space between the walls.Flanges 210 meant for vacuum systems may be used to form a leak proofconnection. The fluid circulation system may have provisions to heat orcool the fluid. Chamber 214, along with its contents, may be cooled orheated through this arrangement.

A control system may include a controller 234 that may communicate withthe various components as indicated by the communication lines. Throughthe lines, the controller 234 may receive information, such as signals,from sensors 236, 237. The controller 234 may signal to one or more ofthe valves 215, 220, 223, 227, 233, which may respond by opening orclosing. The valve 211 may communicate with the controller 234, andthrough which the controller 234 may control the flow of theenvironmental control fluid from the circulation system. Thus, thecontroller 234 may monitor and may control the overall reactionconditions.

Prior to operation, the chamber 214 may be evacuated. The controller 234may activate a valve 227 and a vacuum pump (not shown) to evacuate thechamber 214. The chamber 214 may be flushed with a gas, including aninert gas or a gas such as hydrogen which may be used to remove one ormore contaminants from the chamber 214. The energy source 204 may beactivated to heat, and thereby volatilize, any volatile contaminants.The successive evacuation and purging may remove the contaminants fromthe chamber 214.

During operation, the controller may activate a valve 223 to start aflow of raw material from a reservoir 222 to the crucibles 230 through araw material inlet 224. A dopant may be flowed into the crucible througha dopant inlet 232 in response to the opening of the corresponding valve233. The controller may adjust the rates of flow of materials byadjusting the degree to which the corresponding valves are open orclosed. The controller 234 may communicate with the sensors 236, 237.The temperature and pressure within the chamber may be raised todetermined levels by the controller 234 activating the energy source204, and/or adjusting an outlet valve 227.

Once the desired temperature and pressure has been attained, anitrogen-containing gas may be introduced in the chamber 214 through afirst inlet 216. Alternatively, a nitrogen-containing gas may beintroduced in the chamber in the beginning or at any point during theheating cycle. A halide-containing gas may be flowed in through a secondinlet 218. The controller may adjust the flow rate of these gases bycontrolling the respective valves 215, 220.

The raw material including the dopants may react with thenitrogen-containing gas in the presence of the halide-containing gas.The reaction may proceed until the raw material reacts to form the metalnitride. In the illustrated embodiment, a silicon doped gallium nitridemay be formed.

FIG. 3 is a schematic view of an apparatus 300 detailing the inlets inaccordance with an embodiment. The apparatus 300 may include a housing302 having a wall 304, the wall 304 may have an inner surface 306 and anoutward facing surface 308, as illustrated in the figure. The wall 304may be radially spaced from an axis 309. An energy source 310 may beprovided proximate to the outer surface. The inner surface 306 of thewall 304 may define a chamber 312.

The apparatus 300 may further include inlets 316 and 318. The inlet 316,in one embodiment, may be a single walled tube, and extends into thechamber 312 through the wall 304. The inlet 316 may be nested within,and spaced from the inner surface 306 of the wall 304. An exit end ofthe inlet 316 may define an aperture 322. A baffle 324 may adjoin theaperture 322. The spacing between the inlet 316 and the inner surface306 of the wall 304 may define the inlet 318. Further, an aperture oropening 326 may be provided in the inlet 318. A crucible 330 may bedisposed within the chamber 312.

A halide-containing gas may be introduced into the chamber 312 from asource (not shown) through the inlet 316, and a nitrogen-containing gasmay be introduced into the chamber 312 from a source (not shown) throughthe inlet 318. The inlets 316 and 318 may be configured such that thebaffle 324 provided in the inlet 316 may assist in proper mixing of thegases flowing in to the chamber 312 through the inlets.

The apparatus 300 may further include components not shown in the figuresuch as, a control system including a controller which may control theoverall reaction, valves for adjusting and/or controlling the flow ofmaterials to and/or from the chamber, inlets for introducing rawmaterials, getters, and/or dopants into the chamber, sources from whereraw materials, getters, and/or dopants may be flowed into the chamber,sensors for monitoring the temperature, pressure and composition withinthe chamber, and the like. The working of the apparatus may be explainedwith reference to above described embodiments.

FIG. 4 is a flow chart depicting a method for preparing apolycrystalline group III metal nitride in accordance with an embodimentaccording to the present disclosure. The method starts by providing agroup III metal (see step 402) and a getter in a crucible (see step404). The crucible containing the group III metal and the getter arethen loaded into a chamber or reactor and the chamber is sealed (seestep 406). The chamber is then evacuated, purged, and otherwisedecontaminated to remove trace impurities. The chamber may be evacuated,purged, and otherwise decontaminated prior to or after loading the groupIII metal and the getter inside (see step 408). The environment in thechamber is adjusted to determined levels. The temperature of the chambermay be maintained between about 800 degree Celsius to about 1300 degreeCelsius, and the pressure within the chamber may be equal to or greaterthan about ambient.

Dopants may be introduced in the chamber. The dopant may be introducedas a dopant precursor. The dopant precursor may be flowed into thechamber from a dopant source.

The temperature within the chamber may be raised to between about 800degrees Celsius to about 1300 degrees Celsius (see step 412), and thepressure may be raised within at least one dimension greater than about1 meter, for a period greater than about 30 minutes. Next, anitrogen-containing gas such as ammonia may be introduced in the chamber(see step 410). The gas may be flowed from a nitrogen-containing gassource through an inlet into the chamber. The flow rate of thenitrogen-containing gas may be greater than about 250 (standard) cubiccentimeters per minute.

A halide-containing gas may be introduced into the chamber (see step414). Optionally, the order of the preceding steps may be interchanged.The flow rate of the halide-containing gas may be greater than about 25cubic centimeters per minute. The ratio of the flow rate of thenitrogen-containing gas to the flow rate of the halide-containing gasmay be about 10:1.

The group III metal may react with the nitrogen-containing gas in thepresence of the halide to form a polycrystalline group III metal nitridefrom which most residual oxygen has been removed or sequestered bygettering (see step 416). The halide affects the reaction between themetal and the nitrogen-containing gas in a determined manner. The getterreacts with oxygen to form a getter metal oxide, oxynitride, oroxyhalide, and additionally with the nitrogen-containing gas to formgetter metal nitride and with the hydrogen halide to form getter metalhalide.

The reaction may proceed through a vapor transport and/or a wickingeffect. The metal nitride crust may form on top of the molten metalwithin the crucible. The crust may be slightly porous. The metal may bevapor transported or, if liquid, wicked to the top of the crust throughthe pores and react with the nitrogen-containing gas. The reaction maydeposit additional metal nitride and add to the crust. The reactionproceeds until virtually all the metal has undergone reaction.Additional metal may be flowed into the chamber from the reservoir.

The chamber may be cooled, see FIG. 5, as an example (see step 502). Theexcess nitrogen-containing gas and hydrogen halide flows out from thereaction zone and ammonium halide may condense on cooler regions of thechamber or outlet. In one embodiment, the chamber and an outlet may bekept hot so as to facilitate downstream trapping of ammonium halide; oralternatively a cold wall section may be incorporated to facilitatecondensation of the ammonium halide. In one embodiment, the chamber maybe opened on the outlet side to minimize leakage through the inlet side.The polycrystalline group III metal nitride may be removed through theoutlet side (see step 504).

Optionally, the polycrystalline group III metal nitride formed may befurther processed. In one embodiment, at least one surface of thepolycrystalline group III metal nitride may be subjected to one or moreof scraping, scouring or scarifying. The surface may be furthersubjected to oxidation in air or in dry oxygen and it may further beboiled in perchloric acid. The residual contamination resulting from thepost-processing step may be removed by washing, sonicating, or both.Washing and sonicating may be performed in, for example, organicsolvents, acids, bases, oxidizers (such as hydrogen peroxide), and thelike. The polycrystalline group III metal nitride may be annealed in aninert, nitriding, or reducing atmosphere. The annealing may also beperformed in pure ammonia at a temperature of about 800 degree Celsiusto about 1300 degree Celsius for a period of time in a range of fromabout 30 minutes to about 200 hours.

Other processing may be performed for use as a source material forcrystalline composition growth. For use as a source material, thepolycrystalline group III metal nitride may be pulverized intoparticulate. The particles may have an average diameter in a range offrom about 0.3 millimeters to about 10 millimeters. The pulverizing maybe carried out through, for example, compressive fracture, jaw crushing,wire sawing, ball milling, jet milling, laser cutting, orcryofracturing. Post pulverization cleaning operations may removeadventitious metal introduced by the pulverization operation, un-reactedmetal, and undesirable metal oxide.

In some embodiments, the polycrystalline group III metal nitride is usedas a source material for ammonothermal growth of at least one group IIImetal nitride single crystal. The polycrystalline group III metalnitride is placed in an autoclave or a capsule, as described in U.S.Pat. No. 6,656,615, U.S. Patent No. 7,125,453, and U.S. Pat. No.7,078,731 and in U.S. Patent Application Publication No. 2009/0301388(see step 506). Ammonia and a mineralizer, for example, at least one ofan alkali metal, amide, nitride, or azide, an alkaline earth metal,amide, nitride, or azide, ammonium fluoride, ammonium chloride, ammoniumbromide, ammonium iodide, a group III metal fluoride, a group III metalchloride, a group III metal bromide, a group III metal iodide, or areaction product between a group III metal, ammonia, HF, HBr, HI, andHCl are also placed in the autoclave or capsule (see step 508).

In some embodiments a getter is also placed in the autoclave or capsule.The added getter may be provided in addition to a getter compositionthat may be present in the polycrystalline group III nitride. The addedgetter may comprise at least one of alkaline earth metals, Sc, Ti, V,Cr, Y, Zr, Nb, Hf, Ta, W, rare earth metals, and their nitrides,halides, oxynitrides, oxyhalides, amides, imides, and azides. In onespecific embodiment, at least a portion of the getter is added in theform of a metal and at least a portion of the mineralizer is added as anazide in such a ratio that the hydrogen generated by reaction of thegetter metal with ammonia and the nitrogen generated by decomposition ofthe azide are present in a ratio of approximately 3:1, as described inU.S. Pat. No. 8,323,405. The added getter may be useful for removingunintentional impurities, for example, oxygen, that are present in themineralizer or other raw material. In one set of embodiments, themineralizer comprises an alkali metal and the getter comprises anitride, imide, or amide of Be, Mg, Ca, Sr, Ba, Sc, Y, a rare earthmetal, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, or W. In another set ofembodiments, the mineralizer comprises Cl and the getter comprises anitride, chloride, oxynitride, or oxychloride of Sc, Ti, Cr, Zr, Nb, arare earth metal, Hf, Ta, or W. In still another set of embodiments, themineralizer comprises F and the getter comprises a nitride, fluoride,oxynitride, or oxyfluoride of Ti, V, Cr, Zr, Nb, Hf, Ta, or W. Inanother set of embodiments, the mineralizer comprises Br and the gettercomprises a nitride, bromide, oxynitride, or oxybromide of Sc, Ti, Cr,Y, Zr, Nb, a rare earth metal, Hf, Ta, or W. In another set ofembodiments, the mineralizer comprises I and the getter comprises anitride, iodide, oxynitride, or oxyiodide of Sc, Ti, Cr, Y, Zr, Nb, arare earth metal, Hf, Ta, or W.

After all the raw materials have been added to the autoclave or capsule,the autoclave or capsule is sealed.

The capsule, if employed, is then placed within a suitable high pressureapparatus. In one embodiment, the high pressure apparatus comprises anautoclave, as described by U.S. Pat. No. 7,335,262. In anotherembodiment, the high pressure apparatus is an internally heated highpressure apparatus, as described in U.S. Pat. No. 7,125,453, U.S. Pat.No. 8,097,081, and in U.S. Application Publication No. 2006/0177362A1.The polycrystalline group III metal nitride is then processed insupercritical ammonia at a temperature greater than about 400 degreesCelsius and a pressure greater than about 0.02 gigaPascal (GPa), duringwhich at least a portion of the polycrystalline group III metal nitrideis etched away and recrystallized onto at least one group III nitridecrystal with a wurtzite structure (see step 510). In some embodiments,the polycrystalline group III metal nitride is processed insupercritical ammonia at a temperature greater than about 500 degreesCelsius, greater than about 550 degrees Celsius, greater than about 600degrees Celsius, greater than about 650 degrees Celsius, greater thanabout 700 degrees Celsius, or greater than about 750 degrees Celsius. Insome embodiments, the polycrystalline group III metal nitride isprocessed in supercritical ammonia at a pressure greater than about 0.02GPa, greater than about 0.05 GPa, greater than about 0.1 GPa, greaterthan about 0.2 GPa, greater than about 0.3 GPa, greater than about 0.4GPa, greater than about 0.5 GPa, greater than about 0.6 GPa, greaterthan about 0.7 GPa, or greater than about 0.8 GPa.

Residual getter in the polycrystalline group III metal nitride isreleased into solution gradually, as the polycrystalline group III metalnitride is etched. Once in solution, the getter may react to form agetter metal nitride, amide, or halide. The getter may also bechemically bound to oxygen. The getter may remove residual oxygen in thesupercritical ammonia solution, enabling growth of group III nitridesingle crystals with improved purity.

In some embodiments, the added getter is annealed and/or coarsened priorto substantial ammonothermal growth of a group III metal nitride. Insome embodiments, the getter may be added as a fine powder or may form afine powder during heating in ammonia with a mineralizer present, whichmay undergo undesirable convection throughout the crystal growthenvironment and/or become incorporated into a crystalline group IIImetal nitride as an inclusion. The getter may be consolidated by holdingat a temperature lower than that at which significant group III metalnitride crystal growth occurs, for example, between about 200 degreesCelsius and about 500 degrees Celsius, for a period of time betweenabout 10 minutes and about 48 hours.

The ammonothermally-grown crystalline group III metal nitride may becharacterized by a wurtzite structure substantially free from any cubicentities and have an optical absorption coefficient of about 2 cm⁻¹ andless at wavelengths between about 405 nanometers and about 750nanometers. An ammonothermally-grown gallium nitride crystal maycomprise a crystalline substrate member having a length greater thanabout 5 millimeters, have a wurtzite structure and be substantially freeof other crystal structures, the other structures being less than about0.1% in volume in reference to the substantially wurtzite structure, animpurity concentration greater than 10¹⁴ cm⁻¹, greater than 10¹⁵ cm⁻¹,or greater than 10¹⁶ cm⁻¹ of at least one of Li, Na, K, Rb, Cs, Ca, F,Br, I, and Cl, and an optical absorption coefficient of about 2 cm⁻¹ andless at wavelengths between about 405 nanometers and about 750nanometers. The ammonothermally-grown gallium nitride crystal may besemi-insulating, with a resistivity greater than 10⁷ Ω-cm. Theammonothermally-grown gallium nitride crystal may be an n-typesemiconductor, with a carrier concentration n between about 10¹⁶ cm⁻³and 10²⁰ cm⁻³ and a carrier mobility η, in units of centimeters squaredper volt-second, such that the logarithm to the base 10 of η is greaterthan about −0.018557 n³+1.0671 n²−20.599 n+135.49. Theammonothermally-grown gallium nitride crystal may be a p-typesemiconductor, with a carrier concentration n between about 10¹⁶ cm⁻³and 10²⁰ cm⁻³ and a carrier mobility η, in units of centimeters squaredper volt-second, such that the logarithm to the base 10 of η is greaterthan about −0.6546 n+12.809.

By growing for a suitable period of time, the ammonothermally-growncrystalline group III metal nitride may have a thickness of greater thanabout 1 millimeter and a length, or diameter, greater than about 20millimeters. In a specific embodiment, the length is greater than about50 millimeters or greater than about 100 millimeters. The crystallinegroup III nitride may be characterized by crystallographic radius ofcurvature of greater than 1 meter, greater than 10 meters, greater than100 meters, greater than 1000 meter, or be greater than can be readilymeasured (infinite). After growth, the ammonothermally-grown crystallinegroup III metal nitride may be sliced, lapped, polished, andchemical-mechanically polished according to methods that are known inthe art to form one or more wafers or crystalline substrate members. Ina specific embodiment, the root-mean-square surface roughness of the atleast one wafer or crystalline substrate member is less than about onenanometer, for example, as measured by atomic force microscopy over anarea of at least about 10 micrometers by 10 micrometers.

In another embodiment, the polycrystalline group III metal nitride isused as a source material for flux growth of at least one group IIImetal nitride single crystal, as described in U.S. Pat. 7,063,741 and inU.S. Patent Application 2006/0037529. The polycrystalline group IIImetal nitride and at least one flux are placed in a crucible andinserted into a furnace. The furnace is heated and the polycrystallinegroup III metal nitride is processed in a molten flux at a temperaturegreater than about 400 degrees Celsius and a pressure greater than aboutone atmosphere, during which at least a portion of the polycrystallinegroup III metal nitride is etched away and recrystallized onto at leastone group III nitride crystal. Residual getter in the polycrystallinegroup III metal nitride is released into solution gradually, as thepolycrystalline group III metal nitride is etched. Once in solution, thegetter may react to form a getter metal nitride, amide, or halide. Thegetter may also be chemically bound to oxygen. The getter may removeresidual oxygen in the molten flux, enabling growth of group III nitridesingle crystals with improved purity.

FIG. 6 depicts a block diagram of a system to perform certain operationswithin the context of the architecture and functionality of theembodiments described herein. Of course, however, the system 600 or anyoperation therein may be carried out in any desired environment. Asshown, an operation can be implemented in whole or in part using programinstructions accessible by a module. The modules are connected to acommunication path 605, and any operation can communicate with otheroperations over communication path 605. The modules of the system can,individually or in combination, perform method operations within system600. Any operations performed within system 600 may be performed in anyorder unless as may be specified in the claims. The embodiment of FIG. 6implements a portion of a computer or control system, shown as system600, comprising modules for accessing memory to hold program codeinstructions to perform: providing a gallium-containing group III metalor a gallium-containing group III metal halide into a chamber, thegallium-containing group III metal or metal halide comprising at leastone metal selected from at least aluminum, gallium, and indium (seemodule 620); providing a getter at a level of at least 100 ppm withrespect to the gallium-containing group III metal into the chamber suchthat the getter contacts the gallium-containing group III metal or thegallium-containing group III metal halide (see module 630); transferringa nitrogen-containing material into the chamber (see module 640);heating the chamber to a determined temperature (see module 650);pressurizing the chamber to a determined pressure (see module 660);processing the nitrogen-containing material with the gallium-containinggroup III metal or metal halide in the chamber (see module 670); andforming a polycrystalline gallium-containing group III metal nitridematerial (see module 680).

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. Therefore, the above description and illustrations should not betaken as limiting the scope of the present disclosure which is definedby the appended claims.

What is claimed is:
 1. A method of preparing a polycrystalline group IIImetal nitride material, comprising: providing a source material selectedfrom a group III metal , a group III metal halide, or a combinationthereof into a chamber, the source material comprising at least onemetal selected from at least aluminum, gallium, and indium; providing agetter at a level of at least 100 ppm with respect to the sourcematerial into the chamber such that the getter contacts the sourcematerial, wherein the getter is provided to the chamber via a vaporphase; transferring a nitrogen-containing material into the chamber;heating the chamber to a determined temperature; pressurizing thechamber to a determined pressure; processing the nitrogen-containingmaterial with the source material in the chamber; and forming apolycrystalline group III metal nitride material.
 2. The method of claim1, wherein the getter comprises at least one of an alkaline earth metal,boron, carbon, scandium, titanium, vanadium, chromium, yttrium,zirconium, niobium, a rare earth metal, hathium hafnium, tantalum, andtungsten, a nitride of any of the foregoing, an oxynitride of any of theforegoing, an oxyhalide of any of the foregoing, and a halide of any ofthe foregoing.
 3. The method of claim 1, wherein the getter comprises atleast one of boron, carbon, scandium, yttrium, and a rare earth metal.4. The method of claim 1, wherein the getter is provided into a cruciblewithin the chamber together with the source material.
 5. The method ofclaim 4, wherein the getter is provided at a level greater than about0.1% with respect to the source material.
 6. The method of claim 1,wherein the getter is provided at a level greater than 300 parts permillion with respect to the source material.
 7. The method of claim 6,wherein the getter is provided at a level greater than about 1% withrespect to the source material.
 8. The method of claim 1, furthercomprising supplying a dopant or a dopant precursor to the chamber. 9.The method of claim 1, further comprising contacting the source materialwith one or more wetting agents, wherein the one or more wetting agentscomprises bismuth, germanium, tin, lead, antimony, tellurium, polonium,and a combination of any of the foregoing.
 10. The method of claim 1,further comprising: cooling the chamber; removing the polycrystallinegroup III nitride material from the chamber; providing thepolycrystalline group III nitride material to an autoclave or a capsulealong with ammonia and a mineralizer; and processing the polycrystallinegroup III nitride material in supercritical ammonia at a temperaturegreater than 400 degrees Celsius.
 11. The method of claim 10, whereinthe mineralizer comprises at least one of an alkali metal and analkaline earth metal.
 12. The method of claim 11, further comprisingproviding an additional getter comprising at least one of Be, Ca, Sr,Ba, Sc, Y, a rare earth metal, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W. 13.The method of claim 10, wherein the mineralizer comprises at least oneof a chloride, a bromide, an iodide, and a fluoride.
 14. The method ofclaim 13, further comprising providing an additional getter comprisingat least one of Sc, Ti, V, Cr, Y, Zr, Nb, a rare earth metal, Hf, Ta, orW.
 15. The method of claim 1, further comprising: cooling the chamber;removing the polycrystalline group III nitride material from thechamber; providing the polycrystalline group III nitride material to afurnace along with a flux; and processing the polycrystalline group IIInitride material in a molten flux at a temperature greater than 400degrees Celsius.
 16. The method of claim 1, wherein the getter comprisesone or more of a hydrocarbon (C_(w)H_(y),where w, y > 0), a halocarbonC_(w)X_(z), where w, z > 0 and X is selected from F, Cl, Br, and I), ahalohydrocarbon (C_(w)H_(y)X_(z), where w, y, z >0 and X is selectedfrom F, Cl, Br, and I), phosgene (COCl₂), thionyl chloride (SOCl₂),boron trichloride (BCl₃), diborane (B₂H₆), hydrogen sulfide (H₂S), ahalide of an alkaline earth metal, boron, carbon, scandium, titanium,vanadium, chromium, yttrium, zirconium, niobium, the rare earth metals,hathium hafnium, tantalum, or tungsten, a hydride of an alkaline earthmetal, boron, carbon, scandium, titanium, vanadium, chromium, yttrium,zirconium, niobium, the rare earth metals, hafnium, tantalum, ortungsten.
 17. The method of claim 1, wherein the polycrystalline groupIII metal nitride material is formed downstream from a cruciblecontaining the source material.
 18. The method of claim 1, wherein oneor more of a crucible for containment of group III metal, a reactorhousing wall, a liner for the chamber, a gas inlet to the chamber, abaffle for gas mixing, and a substrate on which the polycrystallinegroup III metal nitride material is deposited comprises a materialselected from tantalum carbide (TaC), silicon carbide (SiC), andpyrolytic boron nitride.
 19. The method of claim 1, wherein one or morecomponents of the chamber are loaded from a glove box before synthesisand the polycrystalline group III metal nitride material is removed fromthe chamber to the glove box after synthesis without substantialexposure to ambient air.
 20. The method of claim 1, wherein: thepolycrystalline group III metal nitride material is a polycrystallinegallium-containing group III metal nitride material; the group III metalis a gallium-containing group III metal; and the group III metal halideis a gallium-containing group III metal halide.
 21. The method of claim1, wherein: the determined temperature is from 800° C. to 1,300 ° C.;and the determined pressure is greater than 0.02 GPa.
 22. A method offorming a polycrystalline gallium-containing group III metal nitridematerial, comprising: providing a gallium-containing group III metal ora group III metal halide source material to a chamber, thegallium-containing group III metal or metal halide source materialcomprising at least one metal selected from aluminum, gallium, andindium; providing a getter at a level of at least 100 ppm with respectto the source material into the chamber such that the getter contactsthe source material; transferring a nitrogen-containing material intothe chamber; heating the chamber to a determined temperature;pressurizing the chamber to a determined pressure; processing thenitrogen-containing material with the source material in the chamber toform a polycrystalline gallium-containing group III metal nitridematerial comprising a plurality of grains of a crystallinegallium-containing group III metal nitride; the plurality of grainshaving an average grain size in a range from about 10nanometers 10nanometers to about 10 millimeters and defining a plurality of grainboundaries; and the polycrystalline gallium-containing group III metalnitride material having: an atomic fraction of a gallium-containinggroup III metal in a range from about 0.49 to about 0.55, thegallium-containing group III metal being selected from at least one ofaluminum, indium, and gallium; and an oxygen content in the form of agallium-containing group III metal oxide or a substitutional impuritywithin the polycrystalline gallium-containing group III metal nitridematerial less than about 10 parts per million (ppm); and a plurality ofinclusions within at least one of the plurality of grain boundaries andthe plurality of grains, the plurality of inclusions comprising agetter, the getter constituting a distinct phase from the crystallinegallium-containing group III metal nitride and located within individualgrains of the crystalline gallium-containing group III metal nitrideand/or at the grain boundaries of the crystalline gallium-containinggroup III metal nitride and being incorporated into the polycrystallinegallium-containing group III metal nitride at a level greater than about200 parts per million,; and; forming a crystalline gallium-containinggroup III metal nitride crystal from the polycrystallinegallium-containing group III metal nitride material characterized by awurtzite structure substantially free from any cubic entities and anoptical absorption coefficient less than or equal to about 2 cm⁻¹ atwavelengths between about 405 nanometers and about 750nanometers 750nanometers.
 23. The method of claim 22, wherein the polycrystallinegallium-containing group III metal nitride material comprises aplurality of grains of a crystalline gallium-containing group III metalnitride; wherein the plurality of grains is characterized by an averagegrain size in a range of from about 10 nanometers to about 10millimeters and defines a plurality of grain boundaries; and thepolycrystalline gallium-containing group III metal nitride material ischaracterized by: an atomic fraction of a gallium-containing group IIImetal in a range of from about 0.49 to about 0.55, thegallium-containing group III metal being selected from at least one ofaluminum, indium, and gallium; and an oxygen content in the form of agallium-containing group III metal oxide or a substitutional impuritywithin the crystalline gallium-containing group III metal nitride lessthan about 10 parts per million (ppm); and a plurality of inclusionswithin at least one of the plurality of grain boundaries and theplurality of grains, the plurality of inclusions comprising a getter,the getter constituting a distinct phase from the crystallinegallium-containing group III metal nitride and located within individualgrains of the crystalline gallium-containing group III metal nitrideand/or at grain boundaries of the crystalline gallium-containing groupIII metal nitride and being incorporated into the polycrystallinegallium-containing group III metal nitride material at a level greaterthan about 200 parts per million.
 24. A method of preparing a group IIImetal nitride crystal, comprising: providing a source material selectedfrom a group III metal, a group III metal halide, or a combinationthereof into a chamber, the source material comprising at least onemetal selected from at least aluminum, gallium, or indium; providing agetter at a level of at least 100 ppm with respect to the sourcematerial into the chamber such that the getter contacts the sourcematerial, wherein the getter is provided to the chamber via a vaporphase; adding a nitrogen-containing material into the chamber;processing the nitrogen-containing material with the source material inthe chamber to form a polycrystalline group III metal nitride materialby heating the chamber to a predetermined temperature; introducing thepolycrystalline group III metal nitride along with ammonia and amineralizer into a container; and heating the container to process thepolycrystalline group III metal nitride in supercritical ammonia to etchaway at least a portion of the polycrystalline group III metal nitrideand recrystallize said at least a portion as the group III metal nitridecrystal.
 25. The method of claim 24, further comprising: removing thegroup III metal nitride crystal from said container and forming one ormore wafers from the group III metal nitride crystal.
 26. The method ofclaim 24, wherein heating the container comprises heating said containerto a temperature greater than about 400 degrees Celsius.
 27. The methodof claim 24, wherein heating the container comprises pressurizing thecontainer to greater than about 0.02 GPa.
 28. The method of claim 24,wherein said introducing includes introducing a second getter in thecontainer.
 29. The method of claim 28, wherein the second gettercomprises at least one of alkaline earth metals, Sc, Ti, V, Cr, Y, Zr,Nb, Hf, Ta, W, rare earth metals, and their nitrides, halides,oxynitrides, oxyhalides, amides, imides, and azides.
 30. The method ofclaim 24, wherein said mineralizer is at least one of an alkali metal,amide, nitride, or azide, an alkaline earth metal, amide, nitride, orazide, ammonium fluoride, ammonium chloride, ammonium bromide, ammoniumiodide, a group III metal fluoride, a group III metal chloride, a groupIII metal bromide, a group III metal iodide, or a reaction productbetween a group III metal, ammonia, HF, HBr, HI, and HCl.
 31. A methodof preparing a group III metal nitride crystal, comprising: providing asource material selected from a group III metal, a group III metalhalide, or a combination thereof into a chamber, the source materialcomprising at least one metal selected from at least aluminum, gallium,or indium; providing a getter at a level of at least 100 ppm withrespect to the source material into the chamber such that the gettercontacts the source material, wherein the getter is provided to thechamber via a vapor phase; transferring a nitrogen-containing materialinto the chamber; processing the nitrogen-containing material with thesource material in the chamber to form a polycrystalline group III metalnitride material by heating the chamber to a determined temperature; andusing the polycrystalline group III nitride material as a sourcematerial for flux growth of at least one group III metal nitridecrystal.
 32. A method of forming a gallium-containing group III metalnitride crystal, comprising: providing a gallium-containing group IIImetal or a group III metal halide source material to a chamber, thegallium-containing group III metal or metal halide source materialcomprising at least one metal selected from aluminum, gallium, andindium; providing a getter at a level of at least 100 ppm with respectto the source material into the chamber such that the getter contactsthe source material; adding a nitrogen-containing material into thechamber; processing the nitrogen-containing material with the sourcematerial in the chamber to form a polycrystalline gallium-containinggroup III metal nitride material comprising a plurality of grains of acrystalline gallium-containing group III metal nitride by heating thechamber to a predetermined temperature, the plurality of grains havingan average grain size in a range from about 10 nanometers to about 10millimeters and defining a plurality of grain boundaries; and thepolycrystalline gallium-containing group III metal nitride materialhaving: an atomic fraction of a gallium-containing group III metal in arange from about 0.49 to about 0.55, the gallium-containing group IIImetal being selected from at least one of aluminum, indium, and gallium;and an oxygen content in the form of a gallium-containing group IIImetal oxide or a substitutional impurity within the polycrystallinegallium-containing group III metal nitride material less than about 10parts per million (ppm); and a plurality of inclusions within at leastone of the plurality of grain boundaries and the plurality of grains,the plurality of inclusions comprising a getter, the getter constitutinga distinct phase from the crystalline gallium-containing group III metalnitride and located within individual grains of the crystallinegallium-containing group III metal nitride and/or at the grainboundaries of the crystalline gallium-containing group III metal nitrideand being incorporated into the polycrystalline gallium-containing groupIII metal nitride at a level greater than about 200 parts per million;introducing the polycrystalline gallium-containing group III metalnitride along with ammonia and a mineralizer into a container; andheating the container to process the polycrystalline gallium-containinggroup III metal nitride in supercritical ammonia to etch away at least aportion of the polycrystalline group III metal nitride and recrystallizesaid at least a portion as the gallium-containing group III metalnitride crystal.
 33. The method of claim 32, further comprising:removing the gallium-containing group III metal nitride crystal fromsaid container and forming one or more wafers from thegallium-containing group III metal nitride crystal.